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[Phys-L] Re: pinhole camera



Pinhole is on bottom of cannister, about 1 mm across. Eye is near this
hole, looking through the cannister at text. Text is about 5-6 cm from eye.

Forum for Physics Educators <PHYS-L@list1.ucc.nau.edu> on Wednesday, June
1, 2005 at 11:03 AM -0500 wrote:
On Wednesday, Jun 1, 2005, at 10:47 America/New_York, Anthony Lapinski
wrote:

You can make a pinhole camera using a small film cannister. Hold it up
to
a printed page. Not only does my near point decrease, but the text also
appears larger.

How am I able to focus more closely on objects? Is it because there is
less light coming into my eye, so it's easier for my eye lens to focus
an
image?

And how does a pinhole camera magnify an object? Is it mainly because
of
diffraction? I usually don't see diffraction mentioned when I read
about
pinhole cameras. The rays drawn are always straight.

The first paragraph above does not help me to deal with the issue.
Where is the pinhole? How large is it? How far is it from the object?
How is the object illuminated? Where is the image formed? The questions
asked can not be answered unless such information is provided.

Ludwik Kowalski
Let the perfect not be the enemy of the good.
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